First step is to choose the right resin. Resin cures are typically either gradual or snap cure. Gradual cure resin will cure slowly and in layers (making it suitable for rotocasting), whereas snap cure resin will remain liquid for awhile, and then solidify quickly.
If working with gradual cure resin then you can usually fill your mold to the desired level, rotocast to achieve the desired thickness, and be finished.
With snap cure resin it is often required to cast in more than one layer. You will need to allow the resin to cool inbetween layers to ensure that the hot resin doesn’t expedite the cure of the next layer. Depending on desired thickness, 2-3 layers might be sufficient.
At SG1Props we have used rotocasting to successfully create parts for the Goa’uld ribbon device, as well as other props.